This application is related to copending application Ser. Nos. 316,380, 316,342, and 316,220, all filed on even date herewith.
1. Field of the Invention
The present invention relates to aromatic polyamide-imide polymers based on amino-monomers containing two hexafluoroisopropylidine linking groups or two 1-phenyl-2,2,2-trifluoroethane linking groups, and having improved physical, mechanical and chemical properties, and to a method for preparing such polymers.
2. Description of Related Art
Polyamide-imide polymers and copolymers are known in the art. These materials are generally prepared by the condensation polymerization of trifunctional acid monomers such as the 4-acid chloride of trimellitic anhydride and one or more aromatic diamines. Examples of such polyamide-imide polymers are disclosed in U.S. Pat. Nos. 3,347,828, 3,494,890, 3,661,832, 3,920,612 and 4,713,438. These polymers may be characterized by extremely good high temperature properties (Tg of about 275.degree. C. or higher), good high temperature stability, good tensile strength at high temperatures, good mechanical properties and good chemical resistance. These polyamide-imides are useful as wire enamel coatings, laminates, molded products, films, fibers impregnating varnishes and in other applications where high thermal stability is required.
One of the problems associated with such polymers is that they exhibit generally poor flow properties which render them difficult to process, particularly to injection mold or to spin into fibers. These polymers are also relatively hydrophilic and tend to absorb moisture which can effect their clarity, heat stability, processability, mechanical and electrical properties.
Attempts have been made in the art to improve the flow properties of polyamide-imide polymers. For example, U.S. Pat. No. 4,448,925 discloses including from about 1 to about 10 percent phthalic anhydride into the polymerization recipe to provide polyamide-imide copolymers having improved flow properties. However, this technique for improving flow properties is made at the expense of the heat stability and chemical resistance of the polymer. Yet another method for improving the flow properties of such polymers is to form blends thereof with up to about 10% by weight of a polyamide polymer such as nylon 6 or nylon 66, as disclosed in U.S. Pat. No. 4,575,924. Once again however, such an approach to solving the flow problem is made at the expense of the thermal stability and optical clarity of the resultant polymer blend.
Copending application Ser. No. 316,380 discloses polyamide-imide polymers prepared by condensing a trifunctional acid anhydride monomer such as 4-trimellitoyl amhydride chloride with an aromatic diamine containing the hexafluoroisopropylidene linking group, such as 2,2-bis (4-aminophenyl) hexafluoropropane (6F-Diamine). These polyamide-imide polymers exhibit excellent thermal properties and also posses improved processability.
Polyamides prepared from so-called 12-F monomers are disclosed in Applicant's copending application Ser. No. 124,744, filed in the USPTO on Nov. 24, 1987. These polyamides may be prepared by forming the polymer condensation product of a 12F-Diacid choride such as 4,4'-bis [2-(4-chlorocarbonylphenyl) hexafluoroisopropyl] diphenylether with one or a mixture of aromatic diamines. Similarly, copending application Ser. No. 124,704 filed in the USPTO on Nov. 24, 1987, discloses polyamide polymers prepared by forming the polymer condensation product of a 12F-Diamine such as 4,4'-bis [(4-aminophenoxyphenyl) hexafluoroisopropyl] diphenyl ether with one or more diacids or diacid halides.